The invention relates to the field of communications engineering and data transmission by means of optical signals. More specifically, the invention relates to a waveguide with a first longitudinal section, which has at least one core with a first refractive index and a sheath with a second refractive index surrounding said core, wherein the waveguide is adapted to guide at least one optical signal in the core.
From U.S. Pat. No. 5,333,218 a waveguide with a core, a sheath and a coating is known. Laser light of a predeterminable wavelength may be coupled into the core of this known waveguide, said laser light being guided by total internal reflection at the interface between the core and the sheath within the core. The outer coating serves to protect the sheath from mechanical damage and contamination.
This known waveguide is tapered conically at one end, with the result that the end side of the waveguide acting as a light exit surface is smaller in size and the angular divergence of the emerging light beam is enlarged. Coupling of optical power between different waveguides or coupling of optical power from an incident free beam into the waveguide may be improved by means of this taper.
Furthermore, it is known from the art to use modulation formats which utilize the modal dispersion of the waveguide to carry information. The known waveguide as outlines above has the disadvantage that the assignment of information carried by different modes guided in the waveguide may be lost at the junctions between different waveguides or at the junction between a waveguide and an optical component. Furthermore, some modes may lay outside the acceptance range of the waveguide, with the result that these modes are lost during coupling-in and thus are permanently removed from the optical signal. Undesired data loss during optical data transmission is the result.
Therefore, it is an object of the invention to improve the coupling of optical power between at least one dielectric waveguide.